The journal Nature recently published an article that argued the gold and silver found on Earth should be much more abundant than they are. Whilst both metals can be found scattered throughout space, they are relatively rare to find on Earth compared to other elements, and the lack of gold in particular has been a growing concern amongst the mining industry. Whilst the metal has always been scarce, it is being found less and less often which will certainly mean an increase in price as time goes on.
Bernard Wood, a geologist from Oxford University, argues that ‘The silicate Earth is strongly depleted in moderately volatile elements (such as lead, zinc, indium and alkali elements) relative to CI chondrites, the meteorites that compositionally most closely resemble the sun’. His paper studies the lack of gold and silver found on the planet, concluding that the way it was formed is the cause of this.
‘Earth’s Volatile Contents Established By Melting And Vapourisation’, as the paper is titled, looks at the formation of the earth and argues that the gold that would have been present at one time turns to gas once it reaches a particular level of temperature. Using a furnace, Wood studies the effects of heat on a model version of an early Earth, using temperatures of up to 1,300 degrees Celsius, as well as adding elements such as carbon dioxide, carbon monoxide, basaltic rock and zinc oxide to the process, to mimic the formation of the planet.
‘Our experiment shows that melting processes explain the pattern [of volatile depletion] perfectly’, concluded the study. ‘We find that the pattern of volatile element depletion in the silicate Earth is consistent with partial melting and vapourisation rather than with simple accretion of a volatile-rich chondrite-like body’.